1. Field of the Invention
The present disclosure relates to electrical conductors and more specifically to a connector for joining two segments of electrical conductors.
2. Description of the Related Art
Most of the developed countries have centralized power generation facilities fueled by carbon-based fuels or renewable energy sources. The electrical voltage generated by these facilities is: stepped up by a transformer; distributed over vast distances via high tension, overhead conductors; stepped down in voltage at a substation; and, finally distributed to individual utility customers. The majority of overhead transmission conductors in use today are aluminum conductors wound around steel-reinforced cores. These are referred to as aluminum conductor steel reinforced (ACSR) conductors. Aluminum material is used for conductors, because of its light weight and low cost when compared to other materials such as copper. ACSRs are designed to operate at upper temperatures as high as 100° C. (212° F.) and, for limited periods of time (e.g., emergencies), at temperatures as high as 125° C. (257° F.). These temperature limits constrain the thermal rating of a typical 230-kV line to about 400 MVA.
ACSR conductors generally span between spaced-apart towers for distances of up to fifty miles or more. Because of these vast distances, individual conductor segments are often joined together by connectors. Tension loads imparted on these connectors are affected by: the weight of the joined conductors themselves; the ambient temperature of the environment; water and ice accumulation; oscillations; and extreme wind loads for example.
A conventional ACSR connector is illustrated in FIG. 1 of the accompanying drawings. Here, a single stage, compression style connector 100 is used to join two conductor segments 102a, 102b having a series of outer conducting strands 104a, 104b coiled around reinforcing inner cores 106a, 106b. An aluminum outer splice 108 and inner core grip or cross wire (not shown) are assembled and compressed together with a hydraulic press and die or, in some cases, imploded together with an explosive charge to gain the required pre load compression in the connector 100. A finite element analysis of the connector 100 from the previous research work indicated that approximately seventy-seven percent of the residual stress at the steel core/core-grip interface is relaxed when the die is removed at the end of the compressing process. For further details of the analysis, please see the following reference [1] Jy-An Wang, Edgar Lara-Curzio, Thomas King, Joe Raziano, John Chan, “The Integrity of ACSR Full Tension Splice Connector at Higher Operation Temperature”, IEEE Transactions on Power Delivery, 2008, Vol. 23(2), pp. 1158-1165, which is hereby incorporated by reference.
Please note that a majority of the electrical current flowing between the two, ACSR conductor segments 102a, 102b is actually transferred through the outer splice 108. Because the outer strands 104a, 104b do not overlap one another in the radial or axial direction, as illustrated by the hidden lines, the current must flow through the outer splice 108. The flow of current through the outer splice 108 increases its temperature and, due to thermal expansion, the outer splice 108 expends in diameter slightly. This slight increase in the diameter of the outer splice 108 reduces the compressive preload of the entire connector 100, which can lead to increased electrical resistance, arching, corrosion and eventually to failure of the connector 100. As a result of ever-increasing power demands, including the operation of transmission lines at higher temperatures, there are concerns about the integrity of compression-type splice connectors.
Despite the teachings of the prior art, improvements in connector design are required to support the increased power demands of the 21st century.